1. In a toaster, the wires that heat up making the toast will glow a red color. In this case, the purpose of the toaster is to make heat and the wasted energy is in the form of light.
   1. If the toaster is 1200 W, what is the resistance of the wires? Assume it is plugged into a 120 V outlet.
   2. How much current does the toaster draw?
   3. How much total energy does the toaster use if it is on for 4 minutes to make a slice of toast?
   4. If the toaster is 95% efficient, how much energy is making heat and how much is making light?

1. The microwave is 1000 Watts. Assume it is plugged into another 120 V outlet in the kitchen.
   1. How much current will the microwave draw?
   2. The circuit breaker is designed to turn off the electricity if too much current is going through a room. If the circuit breaker is designed for a maximum of 20 A, can you use the toaster from #1 and microwave at the same time? Why?
   3. How much total energy is used by the microwave if it is used for 2.5 minutes to make popcorn?
   4. If the microwave is 85% efficient, how much energy is used for making the popcorn and how much is wasted?

1. Old fashion light bulbs wasted a lot of energy by producing heat as well as light. When plugged into a 120 V outlet, a certain bulb draws 0.5 amps of current.
   1. What is the power of this bulb?
   2. If it is on for an average of 4 hours a day for a month (30 days), how much total energy does it use?
   3. If the bulb is only 25% efficient, how much of the energy makes light and how much makes heat?

1. Today we use LED bulbs instead of the old fashion light bulbs because they are about 90% efficient.
   1. Assume the LED bulb makes the same amount of light energy as the bulb from problem 3. How much total energy does the LED bulb use?
   2. If it is on for the same time as the bulb from problem 3, what is the power of the LED bulb?
   3. How much current does it draw from the 120V outlet?

1. The bulb in your phone draws 0.5 A of current and has a resistance of 40 ohms.
   1. How powerful is the bulb?
   2. What is the voltage across the bulb?
   3. If you have it on for 8 minutes, how much total energy does it use?
   4. Phone flashlights use LED bulbs (see #4), how much energy makes light and how much is wasted?
   5. When you started to use the flashlight your were at 64%, when you finished you were at 58%.How much total energy is in a 100% charged battery?